A vehicle sunroof normally consists of a metal or glass part by means of which an opening in the roof panel can be closed partially or completely either manually or by remote control. If the sunroof is power-operated, the drive motor is generally housed directly in the roof itself or in the rear area of the vehicle. The power is transmitted via bowden cables or tensile-rigid or compressive-rigid cables. In addition to this sliding movement in the longitudinal direction of the vehicle, a lifting device is generally provided by means of which the rear edge of the glass part can be raised up above the roof panel.
Where a sunroof is made of glass, there is generally an opaque sliding cover, also called a roof lining part, arranged under the glass part to keep excessive solar radiation out of the passenger compartment. This roof lining part can also be moved either manually or under motor control (power-operated).
In the case of power-operated vehicle sunroofs where both the glass part and the roof lining part can each be moved in the roof opening independently of each other by means of separate drives, the fresh air supply and the amount of incident light can conveniently be controlled individually in the passenger compartment. In practice, however, this control over the settings is subject to certain restrictions. Thus, it must not be possible for the drives to be controlled in such a way that the cover part is wide open but the roof lining part is closed, since the roof lining part cannot permanently withstand the wind load acting on it when the vehicle is in motion.
DE 42 21 043 C2 discloses a sunroof for a vehicle wherein the possibility of a closed roof lining part coinciding with an open cover part is excluded by the control device. By this means weather conditions and air stream cannot damage the roof lining part if the cover part is open. A closed roof lining part would in any case not allow any increase in the air circulation in the passenger compartment. The movement of the cover is linked to the movement of the sun shade part in such a way that, when the switch is operated to open the cover, this results not just in the opening of the cover, but also in a selective opening movement of the sun shade part such that the sun shade part assumes a partially open position according to the position of the cover.
Although this linking of the movement of the sun shade part to the movement of the cover, wherein first the cover is moved and only then the sunscreen, protects the roof lining part from wind load in the middle of the sliding range, it is not felt by many vehicle drivers to be optimal in respect of driving comfort. If, when the vehicle sunroof is opened from a fully closed position, first the cover part is pushed back and only then the sunscreen, this sequence of movements does not seem to be in accord with the subjective expectations of many vehicle drivers. The same applies to the closing operation, where the sliding movement of the transparent cover part is detected through the initially only slowly reducing wind noise.
This linking is, however, also disadvantageous if the movement operation during opening or closing of a vehicle sunroof is to be better adapted to the respective climatic region in which the vehicle is predominantly used. For example, in a sunny, hot climate it can be desirable if a partial opening of the cover part simultaneously, by the linking of movement, also causes the sunscreen to follow only a short distance behind the cover part. Conversely, where the vehicle is used in cooler regions with lower levels of solar radiation, it can be felt to be thoroughly pleasant if an opening operation of the cover part, once triggered, simultaneously also opens the roof lining part by a correspondingly great distance, so that right at the starts of the movement more light enters the passenger compartment.
As the individual perception with respect to the linking of the opening and closing movement of the cover and roof lining part varies greatly from person to person, it is essentially desirable that a lag between cover and sunscreen can be adjusted by a control device in the passenger compartment.